Crystal support



April 1953 w. IANOUCHEVSKY 2,831,989

CRYSTAL SUPPORT Filed Feb. 17, 1955 INVENTL'IR fllmo u/ckevoky 5/ I United States P ten 055 q 2,831,989 Patented Apr. 22, 1958 r 2,831,989 CRYSTAL SUPPORT Wladimlr Iano'uche'vsky, Paris, France, assignor to Quartz et Electronique, Asnieres, France, a corporation of France v I I Application February 17, 1955, Serial No. 488,948 4 Claims. 01. 310-91 It is well known that the quality of a piezo-electric crystal depends in large part on the manner in which the crystal is suspended.

In present piezo-electric technique, quartz crystals are used in the form of small discs having electrodes formed by an extremely thin metal coating deposited on the crystal by evaporation in vacuo or by particle bombardment.

Usually the diameter of the metallic coating deposited over each face of the crystal is substantially less than the diameter of the disc. In order to ensure electrical connection with the connector terminals of the support, narrow strips are provided which extend the metal coating as far as the periphery of the disc.

Secured to the terminal pins of the support are connecting wires terminating in a pair of loops. The quartz disc is pinched or clamped betweenthese loops of wire at the points where the strips terminate.

Because such contact is insufiicient the contact surface is coated with a conductive cement which usually comprises a fine powdered silver andBakelite mixture.

' The suspension system just described has serious drawhacks, for two reasons:

(1) The conductive cement is not a pure metal and therefore introduces an additional resistance which is variable with time and temperature conditions, thereby aifecting the over-voltage coeflicient of the crystal.

(2) The connections supported by the quartz disc between the loops of wire exert a mechanical force on the crystal, usually a twisting couple, which also is variable with time and temperature.

Vibrations are also apt to modify the mechanical strain sustained by the quartz.

This invention has as its object to eliminate the difiiculties just mentioned.

It is an object of the invention to provide a support for a piezo-electric crystal, whereby the crystal is maintained without being subjected to any mechanical stresses or strains liable to afiect the oscillations generated thereby.

It is also an object to provide a crystal mounting such that the piezo-electrical characteristics of the crystal will remain constant with time and also with varying temperatures.

It is also an object of the invention to provide a crystal mounting device which Will be unaffected by vibrations even over long periods of time.

Another object is to provide a crystal mount which will be easy to construct and will provide for ready positioning of the crystal in its support. I

In the ensuing description, made by way of example, reference is had to the accompanying drawings, wherein:

' Fig. 1 is a front elevational view;

Fig. 2 is a side elevational view;

Fig. 3 is a view of a supporting member on an enlarged scale;

Fig. 4 is a front view of the support prior to the mounting of the crystal therein;

Fig. 5 is a diagram;

Fig. 6 is a similar diagram relating dition. l i a 'The crystal disc 10 is supported from three points a, b and c on the nodal plane. As an illustrative example of an operative embodiment of the invention, the three points may be physically defined by parts having a circular configurationin cross section. One such part is shown at- 11 and is formed with two similar frusto conical surfaces 12 and13 having aligned axes, connected at their smaller diameter ends to provide a spoolshaped member. The part is formed with an axial bore and through the bore is threaded one leg 14 of a rod or wire 15 formed with a bend 16. The rod 15 is rigidly connected with the spool member 11 either by means of an adhesive bond or by a force fit of the leg 14 into the bore of the spool member. I

The parts such as 11 are made from a material possessing substantially less hardness than the crystal so as to prevent the transfer or coupling of energy to the support and avoid damping the crystals oscillations. Thus the parts such as 11 may be made of plastic material.

to another con- The rods 15, 15 and 15" having the members 11, 11'

and 11" fixed to the ends thereof possess some inherent resiliency. Thus theymay consist of annealed lengths of wire having low stifiness. The wires or rods are secured to a post 17 projecting from the base 18. The wires 15, 15 and 15" are secured to the post 17 as by solder or by being clamped between a pair of metal strips.

The free ends of wires 15, 15 and 15 or more precisely the throat sections of the spool members, substantially define the apices of an isosceles triangle as illustrated in Fig. 5.

In order to insert the disc 10, the legs 15 and 15 are spread apart, this being made possible owing to their resiliency; then the disc is inserted and'applied over the spool member 11", whereupon the legs 15 and 15' are released to' retain the disc under the slight pressure exerted by the spool members 11 and 11 secured on said legs.

The isosceles triangle having the base m, formed by the sections 19 when the disc is not in place, becomes changed to an isosceles triangle as illustrated in Fig. 6 wherein the side 11 is larger than the original side In.

The electrical contact between the extremities of the metal-coating strips 20 and 21 and the pins 22 and 23, is provided by two conductor wires 24 and 25 soldered at one end to the pins 22 and 23 and at the other end to the strips coated on the surface of the crystal.

A similarmethod of suspension embodying parts which provide a mechanical engagement with the crystal in the form of frustoconical elements arranged inopposed relationship and secured on resilient wires, may be applied in connection with the suspension of rectangular crystal elements, by the use of four or six suspending legs. The method may likewise be used in suspending crystal elements of diiferent configuration, by appropriately modifying the shape of the legs and increasing their number where necessary.

What I claim is:

l. Piezo-electric device comprising a plate-like piezoelectric crystal and holding means including three holding elements for holding the plate-like crystal cooperating exclusively with the edge thereof, a first electrode on a face of the crystal and a second electrode on another face of the crystal, a collar supporting said holding means, and means electrically connecting the electrodes and the collar.

2. Holding device for a piezo-electric crystal comprising a collar, a first holding element fixed on said collar having two faces inclined to one another to cooperate with the edge of the crystal for the support of the same two other holding elements each including two faces inclined with respect to another to cooperate with the edge of the crystal, means fixed to the collar each including one of the second-mentioned holding elements, the same being placed at a greater distance from the collar than the first holding element. i l 1 1 3. Holding deviceaccording to claim'2, in which resilient wires are fixed to the collar and in which each of the second-mentionedholding elementsis carried at the end of one of the resilient wires, the resiliency of the wires assuring engagement of the holding elements against the edge of the crystal.

4. Holding device for a plate-like piezo-electric crystal comprising a fixed collar, 9. first holding element including two frustro-conical surfaces securedat their small 4 bases, two other holding elements constituted by two frustro-conical surfaces secured at their small bases, the said common bases of the three holding elements being disposed in a common plane.

References Cited in the file of this patent UNITED STATES PATENTS Whitby Dec. 21, 1954 

